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Download Using Tree Rings to Reconstruct Past Climates
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54 Using Tree Rings to Reconstruct Past Climates Dendroclimatology is the study of the relationship between tree growth and climate change. As a tree grows, it adds one ring for every year of growth. The width of each growth ring depends on a number of environmental factors, primarily temperature and precipitation. Tree rings are a type of proxy data: wide rings suggest wet years, while narrow rings imply dry years. The growth rings in a living tree represent a record of the recent past. Since trees subject to similar environmental conditions produce similar growth rings, comparison of growth rings between trees of different ages, a process called cross-dating, allows the data record to be extended into the distant past. Scientists match a sequence of tree rings in one tree or log with those in another tree or log to extend the record. Douglas-fir tree rings from southwestern New Mexico. 1740 1770 1800 Year 1830 1860 Variance 1.5 Dendroclimatology has been used to reconstruct El Niño variability over the past 700 years. El Niño has a significant impact on precipitation in Oregon. The red line reflects direct instrumental measurement, while the blue line reflects precipitation estimates determined using tree ring data. 1.0 0.5 1300 1400 1500 1600 1700 Year 1800 1900 2000
